2,2&#39;-dihydroxy-4, 4&#39;-substituted benzophenones as ultraviolet absorbents for gr-a rubber



No Drawing. Application February 10, 1954 v serial No. 40?,536

SJCIaimS. cl. ate-43.95

This invention relates to 2,2'-dihydroxy-4,4-substituted benz'ophenone's as ultraviolet absorbents' for preserving organic substances which tend sdrpt'i'on of ultraviolet light.

Various organic compounds exhibit the power to absorb light rays within the band of 2900 to 3700' A., and when uniformly distributed through a transparent plastic Sheet, the resultant sheet acts as a filter for all the light rays passing through and will transmit only'those waves which are "not absorbed by the sheet and/or the absorbing agent. Thus,'it'is'possible'to screen out undesirable light rays and utilizethe resulting filter in many technitfajl and commercial applications, such as "wrapping tissues tortood products'and the like. "'Ma'ny'organic-compounds, such as 2,4"-dihydroxyben'- zophenone, '2,5 dihydroxybenzophenone, 4',4-dih'ydroxyto deteriorate by the abbcnzophenone;"2,2-d'ihyd-roxybenzophenone, and the like have been suggested as'absorb'ents forultraviolef light in various trans arent plastic. sheet materials andthe stabilization of transparentplastics. 'Whe'nf2;i-d ihydroxyb'enzophenone is employed for the protection of polymeric vi'nylidene? chloride products against darkening and embrittling' effects of ultraviolet light-,"considerahle discolorationof the product ensues; The 4,4'-isomer is substantially inetfective when employed irr'the sarn'e products for the same purpose, and the 2,2fand 2,4'-isomers are only slightly effective as ultraviolet absorbers. fThe latter isomer is ineffective in filter coati'ngs'preparedtrom lacquers containing a cellulose ester,. since' the filter has a cut-off at about 290 m In other words, 'the' i'somerabsorbs' none of the ultiavio'letlight of wave length'above 330 m and as a consequence I the filter containing it is practically transparent to all of the ultraviolet light which is normally present in sunlight at sea level. i

2,2,'-dihydroxybenzophenone is of limited value in certain types of transparent plastics. While it inhibits the physical breakdown of plastics and other materials in which it is incorporated, it is not satisfactory as a protective material against ultraviolet fading. In other words,- this compound is. not satisfactory as a protective material against ultraviolet light fading when employed in substantially colorless plastics, resins, film forming materials, colored textiles, and the like. In some cases the colorless. plastics and the like coated with said materials containing this compound become colored after several months. In other cases, slightly colored plastics or film forming material is itself discolored when exposed to ultraviolet light, and in still other cases, the plastic or film forming medium offers no protection to the colored object of its transmission of, ultraviolet light.

We have discovered that 2,2'-dihydroXy-4,4substituted benzophenones, wherein the 4 and 4' substituents are either hydroxy or alkoxy, are not only compatible with varioustypes of substantially colorless film forming plasf tics, resins, gums, waxes, and the' like. to'yicld ultraviolet absorbing compositions, but that their efiiciency at 40f0i 2,753 l Patented Mar. 3,195xfi9 the is about-twelve times that of any other stable compound currently used as an ultraviolet absorbent.

' '4-be'nzoyl resorcinol p'roposedby the prior art is unique in that it exhibits unusual ultravioletabsorbing properties when incorporated into light transmitting carriers or other cojr'np'ofsfitio'ns which have a tendency todeteriorate by the absorption of ultraviolet light or prolonged exposure thereto without impairing the stability of the carrier or eqinpq itionirrwhieh it is incorporated- We have discovered that the aforementioned 2,2 '-dihydloXy 4,4'-s'ubstituted benz'jophenon'es are not only compatible (i; je. dispersibl'e or soluble in)' with various types of 'substantia'llycolorless film forming plastics, resins, gumsfwax s, etc, but also in any, type of organic compo'sitionwlii'ch has a tendency to 'degrate or discolor by ex osure to ultraviolet light. Compounds of this type are especially; adaptable to yield ultraviolet absorbing compositions because of their etticiefncy at 400 Ill 1. which'is about. twelve times that of 4-benz'oy1' resorcinol or any other stable compound currently used as ultraviolet absorbents.

Accordingly, it is an object of the present invention to provide ultraviolet absorbingtcomp o'sitions of matter comprising an organic substance orcomposition containing, in an ultraviolet absorbing amount, 2,2'-dihydroxy-4,4-substituted benzophenonel l Another object is to provide a new class of ultraviolet absorbents which, when present in. very low concentrations, have the characteristic property of retarding degradation and discoloration of'organic substances and compositions which tend to so degrade and discolor upon exposn je: to'ultraviolet light.

Other objects and advantages will appear hereinafter.

The above objects of the present-.iiivention are attained byyincorporating. into an organic substance'orwompo'si tion, an ultraviolet absorbing amount of 2,'2-dihydroxy 4,4'-substituted benzophenone, hereinafter. referred to as ultraviolet absorbents. Compounds: of this type are advantageously employed in practically any type of organic material which is susceptible todegradation or discoloration such as, for example, rubber compositions comprising india rubber, balata,. gutta percha; synthetic vulcanizable products, o g., polychloroprene, olefin p'olysulfides, pol-ybutadiene,butadienfiestyrene copolymers. such as 'Buna ,S butadiene-aerylonitrileeopolymers such as Buna N' and the like; .whether or-not the same have, been admixed with the conventional fillers, pigment, curing agents and the like. All of these rubber and rubber-like materials are characterized by a high elasticity, indicated by a high percentage of extensibility under load and favorable retraction to approximately original size and shape when the load. isremoved, and-in addition a good tensile strength, goodv fiexure and abrasion resistance, and reactivity with sulfur; The proportion of the' ultraviolet absorbent employed. may range from 0.1% to 5% and is mixed with rubber. or rubber-like material in powder form or in solu tion in a suitable solvent, such as. those subsequently referred to, before vulcanization. Since these ultraviolet absorbents have substantially no accelerating eifect, there isno need for adjustment of vulcanizing conditions.

'When employed in l'-2% concentration, the ultraviolet absorbents of. the present. invention not. only serve as age resistors for improving the age-resistance of treated rubher or rubber-like stocks, but also show the unexpected characteristics of providing a very valuable increase in the flex-cracking resistance of the stocks to which they 'are added.

In'white' stocks, the ultraviolet absorbents of the present invention, in contrast. to many of the commercial ultraviolet 'absorbents, do not stain the" treated rubber orrubber-like stock either when the stocks are exposed to direct sunlight or ordinary difluse'd light,-whereas,prior.

ultraviolet absorbents have the very serious fault of producing a highly objectionable discoloration of the treated rubber stocks under the influence of sunlight.

The ultraviolet absorbents may be employed in any type of drying oil composition, such as paints, enamels, varnishes, etc., as well as in the drying oils such aslinseed oil, tung oil, etc., used in their manufacture. Their action in quick drying compositions, such as paints and varnishes is to prevent the breakdown of the filmafter drying and exposure to light; also discoloration by ultraviolet light of the covered surface.

The ultraviolet absorbents of the present invention mix readily, either by solution or by dispersion, with any type 1 of organic material. If the material to which they are added is a liquid such asessential oils, solutions of dyes or pigments, paints, varnishes, enamels, lacquers, drying oils, colored cellulose ether or cellulose ester dopes, and the like, the ultraviolet absorbent is dissolved in any one 1 or a mixture of the following solvents and the solution thereof mixed with the liquid material. The selection of the proper solvent or mixtures thereof will, of course, depend upon its solubility in or compatibility with the liquid material which can be readily determined by simple routine tests:

Acetone Ethanol Propanol Cellosolve Dimethyl dioxane Dioxane Ether Ethyl acetate Methanol Methyl carbitol If, on the other hand, the material to which the absorbent is added is a solid such as colored soap, rubber, rubber-like materials, film forming plastics such as, cellulose In the case of face creams, especially foundation creams for face powders, the absorbent has a beneficial action in preventing sunburn. In lotions they may be employed as tinctures or dispersed in mineral or vegetable oils, with or without the presence of perfumes and/ or dyes, and used as sunburn preventives. Ointments prepared from polyvinylpyrrolidone, containing dispersed therein 0.1%' to 2% of the absorbent, may be used not only as sunburn preventives but also against harmful radiations of the infrared type and atomic fission radiations. The base of the ointment, i. e. polyvinylpyrrolidone and the absorbent appear to exert a synergistic effect with respect to infra-red and atomic fission radiations.

Colored soaps are not so much in, demand today as white soaps. However, in cases where the soap contains a germicidal or bactericidal compound, pleasing dyes or coloring matters are usually added to mask the germicidal compound employed. For this purpose dyestuffs are generally preferred to pigments. The dyestuffs, such as, for example, Ultramarine blue, Methyl violets, Alizarine or .naphthol compounds of chlorophyll,- Chrysoidine, diazamine compounds, paramine compounds, Bismuth brown, Saffranine, and the like, however, are unstable upon prolonged, exposure to any light containing ultraviolet radiations. In such preparations the ultraviolet absorbents of the present invention are exceedingly beneficial since they inhibitfading and discoloration of the soap. The ultraviolet absorbents also stabilize bath preparations such as bath salts containing dyestuffs, especially basic dyestuffs, such as, Auromine, Acridine orange, Chrysine, Phenyline brown, Methylene ,blue's, basic' greens and the like. Of these. the blues and greens are not very stable, and to .obtain good results the'cosmetician usually resorts to the acetate, cellulose formate, cellulose propionat'e, cellulose butyrate, cellulose acetate-propionate, cellulose acetatebutyrate, cellulose nitrate, polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, copolymers of vinyl chloride and vinylidene chloride, polyvinylpyrrolidone, various resins, waxes, and'the like, the absorbent is incorporated by either milling or mastication in powder form, paste form, solution form, and the like. In the case of cellophane, polyethylene, cellophane (regenerated cellulose) and other sheet plastics employed for covering,

or packaging various items such as foods, etc., the absorbent may be incorporated into solutions or do'pes of such plastic materials. The absorbents in solution form are readily applied to colored textiles, colored objects, such as, color photographs, and oil paintings which are r olrlmally exposed for prolonged periods of time to sun- The absorbents are also adaptable for incorporation into various substantially colorless resinous and plastic film-forming materials which are normally cast from solutions, extruded, or laminated into sheets, films, and foils which may be used as such or employed in the preparation of light transmitting carriers as transparent interlayer laminae in safety glass and other structural materials. They are of particular value in the glass fiber, interlayer, laminae, of transparent plastic sheets cast from acrylic resins, phenol-formaldehyde resins, polystyrene resins, cellulose acetate-butyrate, and the like. In this application the glass fiber, laminae, is impregnated with a solution of the absorbent and the fiber allowed to dry prior to lamination.

They are especially adaptable in perfumes, colognes, toilet waters, cosmetics, soaps, creams, ointments, lotions, etc. Many of these preparations because of their coloring matter or dye content fade and discolor by prolonged exposure to sunlight. The addition of the absorbent into such preparations stabilizes them not only from discoloras tion but also from degradation and deterioration.

use of vat dyes. These are added to they saturated solutioniof the salt whereby thecolor is absorbed by the crystals when formed. Many'of the-vat dyes also fade and discolor when exposed to light containing ultraviolet radiations and must be stabilized. t

- :Toilet waters, colognes, perfumes, brilliantines,,and the like, containing either vegetable, basic or vat dyes, are readily stabilized against fading and discoloration by the employment of the ultraviolet absorbents of the present invention. 1

v The ultraviolet absorbents of the present invention are uniquely adaptable for the preparationsof suntan lotionsbecause of theirefliciency at 400 mu.

The ultraviolet absorbents of the present invention are not only suitable for incorporation into various types of cosmetic preparations, but also into the individual components or constituents ofcosmetic prepara tions, such as, essential oils, for example, Ajowan oil, Rose Geranium, Bitter Almond, Eucalyptus, Ganetheria, Palma Rosa, Anise, Rosemary, Lavender, Sassafras, Angelica and the like, all of which have the tendency to discolor and degrade when exposed for prolonged periods of time to ultraviolet radiations. Their tendency to such degradation is readily minimized and in many cases completely prevented by the addition of a small quantity of ultraviolet absorbents of the present invention.

The proportions of the absorbents or mixtures thereof are not critical and may be employed in concentrations ranging from l-2%. The exact amount to.be em: ployed for any particular composition is readily ,determinable by trial experiments. For practical purposes we have found that concentrations ranging from 0.1-0.5 based on the weight of the organic composition to be stabilized yield compositions that satisfactorily resist discoloration and degradation when exposed to sunlight. It is to be notedthat each type of organic material to be stabilized mayrequire an amount of the absorbent or mixture of absorbents which will differfrom a closely anala'gous material, and as noted above the actual amount employed will depend upon the nature of the material, and the method of dispersion or solution assesses a]. experiments.

' Wehave prepared compositions containing as much as of the ultraviolet absorbents with excellent stability and by dilution obtained compositions in which the concentration was reduced to 0.1%. The finalv products also were stable against discoloration and'degradation. In other words, these experiments conclusively showed that the amount employed is not critical, and when employed in excess has no deleterious etfe'ct in the composition or upon the composition. itself. The only exception being when incorporated into compositions, preparations and the like which are normally white, whereby a slight yellowish. discoloration. isadded to such compositions when the amount. of the'ultraviolet absorption exceeds 5% based on the weight of therna terial stabilized. "1'n addition to the foregoing. uses, the; ultraviolet absorbents may also be employed: durin'g'the manufacturing steps of. preparing artificial yarns, lacquers, molding compositions and impregnated textiles, laminated prodnets, and. the like. The absorbents of the present invention are characterized by the following general formula:

HO OH I I f l wherein R is hydrogen or alkyl; e. g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, 'isoamyl, hexyl, heptyl, octyl, octadecyl, lauryl and the like.

' The compounds characterized by the foregoing general formula are prepared according to the methods disclosed in application, Serial N0124'5;643, filed on September 'Z'," 1951, by Wynn" and Hoch, for 2,2,4-trihydroxy-4"- alkoxybenzophenones and process of preparing the same, application; Serial No. 214,828 filed on March 9, 195'l,'by Hoch for 2,2'-dihydroxy=4,4'-dialkoxybenzophenones and the. process of preparing the same, and the 2,2,4,4'-te trahydroxybenzophenone is prepared according to the method of either Meyer and Conzetti in Ben, 30, 969973 (1897) andShoesmith and Holdane in J. Chem. Soc.,. 125, 1 13 (.1924). By reference thereto various specific examples are disclosed and the manner of their preparation. All. suchdisclosed compounds may be employed as such individually or in admixture. We have also found that mixtures'containing from 55 to 75% by weight of 2,2,4- trihydroxy-4-alkoxybenzophenone, to 25% by Weight of.2,2'-dihydroxy-4,4'-dimethoxybenzophenone and 10 to by weight of 2,2,4,4'-tetrahydroxybenzophenone are-equally as effective as each one of the individual components when employed as ultraviolet absorbents. Such admixtures may be obtained when 2 molesof resorcinol dialkyl ether are allowed to react with 1 /3 moles of phosgene in the presence of 2 moles of aluminum chloride. Care should be taken not to use additional aluminum chloride, since it tends further to d'ealkylate the dihydroxy component to the trihydroxy component and the trihydroxy component to the tetrahydroxybenzophenone. The mixture of the latter components requires one-twelfth the concentration of 4-benzoyl resorcinol for a 50% transmission. cut-off at 400 m In view of. this property smaller quantities may be employed ranging from 0.1 {01%; k.

Instead of using the mixture obtained by the aforesaid condensation reaction, the individual components as pro pared according to the references referred to above may be mixed in the proportions stated. It is to be noted that the mixture and the individual components are equally efiective when employed as ultraviolet "absorbents in the materials and compositions of the present invention.

The following examples. will illustrate the various organic compositions containingthe ultraviolet absorbents of the present inventionand the mixtures thereof.

,6 emu e It (Toilet water) A composition v n i seam" t isl' ewins formula Percent by weight Ethyl alcohol .i' 542800 Perfume oil 11000 2,2',4-trihydroxy-4-methoxybenzophenone 0.005 Water 42.395 Glycerine 1.800 Blue dye, .Trace Yellow dye Trace ismadeup' as'folToWs:

A conventional. violet type perfume; oil. and 2;?;' ,4'-trihydroxy-4'-methoxybenzophenone. were. dissolved in: the alcohol base. The water and glycerine w'erei weighed-1 to? gether and slowly added. to. the alcohoL-penfumeand 2,2f,4-tr ihydroxy-4T-methoxybenzophenone mixture: The desired colors intheconventional small proportions were then added and the toilet water, composition was. chilled and filtered.

After 20 hoursexposurej in the fiadeometer the product showed little change incolor. 'A control" samplefcoiitaining all the other ingredients except the 2', 2,4-"trihy} droxy-4'-methoxybenzophenone faded completely under the same conditions. EXAMPLE II iumd' A composition haying substantially the following formula:

Percent by weight Ethyl alcohol (95%) 87.995 Perfum'e'o'il [125,000 2,2,4-trihydroxy-, 4'-ethoxybenzophenone 0.005 Blue dye" Trace Ethyl alcohol (S. D. 40)' 5428,00 Perfume oil" I M .0500 y 'enzophenone 0.005 Boric acid t 0250 Water 4 Glycerine' .2000 Blue dye Trade Yellow dye Trace was made up essentiallyas in Example I except that the boric acid component was. first added; to. the water with the glycerine. This composition showed excellentcolor; stability in the, fadeometer.

EXAMPLE IV "mall-ails...) A brilliantine of thefollowing formula:

r I l B rqsn iw i l Propylene glycol monolaurate' nu; 5.00 m'A-tr ydrox -met x pzophen ne 0.231 Perfume I .1 3 Mineral oil (a refined white o'il) 89.67. Yellow dye (0.1% solution in mineral oil) 2.00

Orange dye (0.1% solution in mineral}oil)-;; i-.. 2100 was nremecl q lbusi II I I esteem ,I

' eats-wa r 'i-:j s h u n i ijd ee a in the r main er a e g edie ts, The c I .I r pertume were dissolved r I th'epropylene glycol monosolution wasstlrre d and a portion thereof; castion ga i I I f i I gla r te an the ssu tmem xtmg was; .then dissolved a polished metaIlicisui-tace. f er drying the foilfsho ved: E l j the m neral oil whereupon the two dyes were introduced i i l jexcellen't gultrgaviolct; absorbentpropert iea and af 24/ 5 y I I I I I n o h m xture and snr red After'24 hours in the-fade hours in the jfadjeomiete'r jrefmjainectelear without; any; I

' ometer the ibrilliantine' remained clear and; the: color. ye11 w ing I I I I I I I I I I I I I I I I I changed: only very slightly. I I I I I EXAMPLEVI IL I I I I i I I I H i i (Dope folcastingtrausparent ultraviolet absorbing; film), I I I I I I I I I '(Amlpsunbum land) I V i i t A composition having substantially. the following I mmwsifim having ub a a l h 'f l r-- I formula; I I I I I I v, a f.

. I I I I Percent hy'weight i Cellulose 'acetatessc cs-e;.. a,- 15.00 Y /Jjfl I I 40.00 15ITriphenylphosphate s c 3 .7 5 i i I Wa e a, I I I I l 4000 I Methyl Cellosolven; t;. ....I 28.69 I j 1 g E byi alcohol(95%)-;-c....... '15;O0 I I Absoluteethyl acetate I i 38.21 it s a hf II I I 2.00 Absoluteethylaleohol; 14.00

' I I Agar-agar I I I i i j I I I I 100 I 1 2,2g4,!l'-tetrahydroxybenzophenone 0.35 i I I 21 :31PM???'i il imt im" 9: was; a -p stes by d s t ne ha ben h ne ein mehfl I I i I I I W i P P l I 19375? 3 I: I I i I I 1 I I I I I l g l i I I 1 I I I I C'ellosolve and incorporating the solution into the dopeof v i i I "The g r i n h 'andi agar-agar:were soakedwith i i f the Icelluloseacetatefcontainingthe remainderofthe in I f j 3 t he sgvv'a'ter until amucilaginous body was Obtained. 3 The: I gredienta; Upon castingaloil. was obtainedwliich when 1 I I benzophenoneiwas' dissolved; in; ethyl aleohol and the 5 I I I I I I I I I) subjected to the fadeometer tor 1000 hours showed no f j 1 I -1jut1on'poured into the'mucilaginous body and the whole 5: diseolorationf,.whereas a 'sitni-lar foilcontaining no benzjo i fs'tiirretl until'a uniform composition wasobtained. There-I i phenoneshowedmarkeddiscol tion after 20fh0tu'st: :g u atter-thelcerinetwas,addedwithstrr" Zh I I I I I lna tawn- I I .I XAMPLEIX I.

'Ipositesolution. iTh e compositioniin'actual;ap lleati II I I I II I I I I I I i i m n? fi l i i f q f i andipreymtfid I I (Ultravioletlightabsorbing oellttlos acerote varfrrislrl i I ="'Sflflhlllfla I'G lSIIGD-tOXIQBIId-nflllfllfl'tatlngIOIhGISKIH II g i;

I i composition havm'g substantiallytgthefollow ng I I II I I I I m 'lw 3 I I Percentbyweigbt v A composition havingsubsta'ntially itheifollowing for ae fie wloswsst te;-- ----w----.---- I I mu1a;-.I. I I I I I I I Acetone's i' ;.c -001.

, j p' m w gh Methylpi'opionate 48.00 I I Whitewater I v c I I 0 Ethyl'alcohols II II ..v i 8.00 I I I i Cocoa butter; I M 1 Diethylene glycolss- I I 2 I I lanolin;'anhydrous;.;;sL-;;e;. .L t;.LQ.t;i gees; 115m 4ei F h d Y- a a Peanut oiL. i "5O 0 '2,2,4-trihydroxyt methoxybenzophenone 64} I 2.00 I I Moldex I I 2,2,4,4'-tetrahydroxybenzophenone 15 Perfume oil n 290 was I. f b h prepared by dlssolvmg the mixtureo enzop enones Amhydwxy'4 'methoxybenzophenone in 2 parts by weight of diethylene glycol and 10 parts methyl propionate. The solution was then incorporated was prepared as follows:

lulose acetate containing the remainder Thewhite wax, cocoa butter and lanolin were gently into the (1096 Of C61 melted by the application of heat to a liquid stage. The 013 the g e benzophenone, perfume oil and Moldex were then added The dope solution was then stirred and a small portion to the peanut oil and gently heated until solution was 616F505 Cast into a The film Was Subjected t0 effectuated. This solution was then added to the liquefadeometer and showed no discoloration after 1000 fied mixture of wax, cocoa butter and lanolin. When hoursapplied to the skin as a sunburn cream it h w d th While we have disclosed the preferred embodiments of same characteristics as in Example V. In addition, the our invention, it will be readily appreciated by those skilled composition when applied to the skin allowed sweating in the art that y changes and Variations y be made therein without departing from the spirit thereof. Ac

to take place.

I EXAMPLE VII cordingly, the scope of the invention may be limited solely by the appended claims. (Lacquer) We claim: l A composition having substantially the following for- 1. An ultraviolet absorbent composition of matter mula: Y comprising butadiene-acryl onitrile copolymer, which Percent by weight normally tends to deteriorate and degrade by exposure to Nitrocellulose 6.00 ultraviolet radiations, having uniformly dispersed therein Ethyl alco 9.00 from 0.1 to 5% by weight of at least one ultraviolet Toluene 23.00 absorbing compound selected from the group consisting Butanol I I II I 6.00 of 2,2,4,4 -tetrahydroxyhenzophen-one and 2,2-dihy- A nsol 10.00 droiiy-4,4dialkoxybenzophenone. Ethyl lactate 3.00 2. An ultraviolet absorbent composition of matter ac- Ethyl 8665816..-.3- -Q... 25.00 cording to claim 1 wherein the ultraviolet absorbing com AJD. M: No. 100 oil 10.00 pound is 2,2-dihydroxy-4,4-dimethoxybenz'ophenone hav Carnauba w 6.00 ing the following formula: t 2,2-dihydroxy-4,4'-dimethoxybenzophenone 2.00

wasprepared as follows no 0 0H t A solution of the benzophenone in ethyl acetate cou- I i--0CH= I taining the carnauba wax was added to the nitrocellulose 7 I I I I l i I 9 3. An ultraviolet absorbent composition of matter according to claim 1 wherein the ultraviolet absorbing compound is 2,2,4,4-tetrahydroxybenzophenone having the following formula:

HO OH References Cited in the file of this patent UNITED STATES PATENTS 2,614,940 Freyermuth et al Oct. 21, 1952 10 Wynn Aug. 17, 1954 1 Hoch Nov. 2, 1954 OTHER REFERENCES 5 Shoesmith: Journal of the Chemical Society, vol. 125

(1924), pages 113 to 115.

Hackhs Chemical Dictionary, The Blakiston Co., Philadelphia, 3rd ed., 1944, page 412.

Giese: American Perfumer and Essential Oil Review, 10 September 1950, page 198. 

1. AN ULTRAVIOLET ABSORBENT COMPOSITION OF MATTER COMPRISING BUTADIENE-ACRYLONITRILE COPOLYMER, WHICH NORMALLY TENDS TO DETERIORATE AND DEGRADE BY EXPOSURE TO ULTRAVIOLET RADIATIONS, HAVING UNIFORMLY DISPERSED THEREIN FROM 0.1 TO 5% BY WEIGHT OF AT LEAST ONE ULTRAVIOLET ABSORBING COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2,2'',4,4''-TETRAHYDROXYBENZOPHENONE AND 2,2''-DIHYDROXY-4,4''-DIALKOXYBENZOPHENONE. 